mongoengine to_json method

# Copyright (c) 2010, Philip Plante of EndlessPaths.com
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def to_json(data, sub_documents=False):
    import copy, datetime, time
    from mongoengine import Document, ObjectIdField
    
    def _convert_to_json(data):
        struct = {}
        ignore = ['_id', 'password']
        for k in data:
            if k in ignore: continue
            value = data[k]
            
            if sub_documents and hasattr(value, "__class__") and issubclass(value.__class__, Document):
                struct[k] = _convert_to_json(value)
            elif isinstance(value, datetime.datetime):
                struct[k] = int(time.mktime(value.timetuple()) + value.microsecond/1e6)
            elif isinstance(value, (unicode, str)):
                struct[k] = value
        
        return struct
    
    return _convert_to_json(data)